Abstract
Objective To assess the influence of alloy composition on the survival of amalgam restorations.
Study selection Data from 14 independent controlled clinical trials on the oral behaviour of Classes I and 2 amalgam restorations, with a follow-up between five and 15 years.
Data extraction and synthesis All data from the 14 trials were cumulated and re-evaluated by secondary analysis. For the analysis, 3119 restorations were available, which were made from 24 different alloys by a group of seven operators. The alloys were divided into four groups according to their zinc content (zinc-containing and zinc-free) and their copper content (conventional and high-copper). During the follow-up of the trials, the restorations were annually assessed for failures, which were classified as to (1) restoration, (2) restorative process and (3) patient-related reasons. With the restoration-related failures, survival functions of the restorations were estimated by alloy and alloy group.
Results The total number of failed restorations was 481, of which 77% were restoration-related and 14% process-related. Eighty percent of the restoration-related failures were due to some form of fracture of the amalgam. Restorations of conventional zinc-free alloys had the shortest survival. After 13 years only 25% survived. Zinc and a high copper content had an equally favourable influence on the survival rate, which was 70% after 13 years when either was present. The highest survival rates were of restorations of zinc-containing high-copper alloys: 85% after 13 years.
Conclusions This analysis suggests that the zinc and copper contents of the alloy influences survival of amalgam restorations.
Letzel H, Van ‘T Hof’ M A, Marshall G W, Marshall, S J. The influence of the amalgam alloy on the survival of amalgam Restorations: a secondary analysis of multiple controlled clinical trials. J Dent Res. 1997; 76: 1787–98
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Address for reprints: Dr G W Marshall, Department of Restorative Dentistry, Box 0758, University of California, San Fancisco, California 94143-0758, USA
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Jokstad, A. The prognosis of amalgam restorations depends on the alloy composition. Evid Based Dent 1, 9 (1999). https://doi.org/10.1038/sj.ebd.6490033
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DOI: https://doi.org/10.1038/sj.ebd.6490033